This relates to an improved method of local radiotherapy, and devices and compositions for accomplishing local radiotherapy.
Radiation has been used for cancer therapy and to control local healing in areas as diverse as preventing excessive scar formation or reducing lymphoid infiltration and proliferation. More recently, radiation has been used to inhibit restenosis following coronary artery or peripheral artery angioplasty. Interstitial radiation by use of radioactivity incorporated into intravascular stents, delivery of radiation dose by use of catheters containing radioactive sources, and external beam radiotherapy have been used.
There are disadvantages to each of these approaches. When radiation is delivered by an extracorporeal beam, the usual problems of limiting the exposure only to those tissues intended to be affected are encountered. Moreover, doses must often be subdivided, requiring more than one visit to the hospital by the patient. If radiation is to be delivered by a catheter or other temporarily-installed medical device, then the rate of delivery of radiation from the device must be high. The active source will normally require careful shielding, even if relatively "soft" radiation, such as beta rays, is used. If administered in the same operation as balloon angioplasty or cardiac bypass, extra complications of an already complex and risky procedure are magnified. Delivery of radiation on a permanently implanted device, or a biodegradable device that necessarily is eroded over a long period of time because it also provides structural support, severely limits the choice of radioisotope because of the need to limit the total delivered dose to the tissue, while simultaneously providing sufficient initial dose to achieve the required effect. Moreover, repetition of the administration, if required, is not readily achieved.
The object of this invention is to provide an improved method for localized radiotherapy for the cure or alleviation of medical conditions.